The power section of a fuel cell power plant will typically be cooled with a recirculating stream of water. The water will be fed through coolant passages in the power section and will be heated therein to a two phase water/steam mixture. The water/steam mixture leaving the power section will then be directed to a steam separator wherein the water and steam in the mixture will be separated from each other. The steam thus recovered will then be routed to the hydrocarbon gas reforming portion of the plant to serve as a reactant for the catalytic reforming of a raw hydrocarbon fuel to a hydrogen rich fuel gas suitable for use in the fuel cell anodes. This type of cooling system requires the use of the aforesaid steam separator, and also requires a water treatment subsystem since the water from the steam separator will be recirculated back through the cooling system. It also requires a separate network of coolant passages in the power section.
It has also been proposed to cool fuel cell power plant power sections by evaporating a water constituent which has been entrained in a gas stream. The gas steam could be an air stream routed through a separate cooling passage section, or it could be one of the reactant gas streams. U.S. Pat. No. 4,678,723 granted July 7, 1987 to R. J. Wertheim discloses one such system. In the system described in the aforesaid patent, water fog is injected into the cathode exhaust, which is then routed through a cooling section in the power section wherein the water is vaporized. The exhaust from the cooling section which contains water vapor is then fed into an auto-thermal reformer.